Deposits on many inner parts of the engine are generally resulted by incomplete combustion of hydrocarbon fuel used for automobile engine. Deposits in the engine degrade the efficiency of the engine. One of these problems is that the resultant hydrocarbon deposit is deposited in combustion chamber, thereby decreasing space in the combustion chamber on compressing the mixture of fuel and air such that a compression ratio is which is higher than the designed one, causing a heavy knocking. Furthermore, continued knocking for a long term causes fatigue stress or abrasion in major parts of the engine. A fuel with high octane number can be used to reduce engine knocking to solve one of these problems but the fuel with high octane number is expensive. The carbon deposit around carburetor prevents air flow on idling or a low speed driving to make a fuel-air mixture containing excessive amount of fuel. These conditions result in incomplete combustion of fuel to make engine idling rough and induce exhausting of excessive amount of hydrocarbon and carbon monoxide.
U.S. Pat. No. 4,881,945 discloses that alkylphenyl poly(oxyalkylene) amino carbamate as polyether amine is effective for controlling the amount of fuel deposit. A desired fuel detergent is obtained by reacting alkylphenyl poly(oxyalkylene) alcohol with phosgene to a chloroformate intermediate, followed by reacting it with polyamine in the above U.S. patent. In the meantime, the phosgene gas is not easy to handle industrially because of its deadly toxicity and a complex process is required to remove unreacted phosgene gas and resultant hydrogen chloride gas.
U.S. Pat. Nos. 4,881,945, 4,160,648, 4,243,798, 4,191,537 and 4,197,409 disclose that 15 equivalent polyamine to chloroformate are used to make monoaminocarbamate and the excessive polyamine should be removed by washing it with distilled water after reaction. In this case, excessive amount of polyamine is used such that it is wasted a lot and should be recovered accompanying an onerous and uneconomic process. Polyamine hydrochloride is obtained in a same ratio with desired aminocarbamate by reaction of polyamine and chloroformate intermediate but the resultant chloride salt is not only bad for a fuel but also causing corrosion and plugging of the apparatus such that it should be maintained in a low level.